# Association of Clinical, Biomechanical, and Psychosocial Factors with Smile Dynamics in Unilateral Cleft Lip: A Multicenter Observational Study

## TL;DR

This study compares smile dynamics in people with cleft lip and non-cleft individuals, finding biomechanical and psychosocial factors influence smiling behavior and quality of life.

## Contribution

The study is the first to associate clinical, biomechanical, and psychosocial factors with smile dynamics in UCL ± P individuals using a multicenter observational approach.

## Key findings

- Participants with UCL ± P showed higher stiffness and tone at the cleft scar site compared to controls.
- Nasolabial esthetics and elasticity correlated with duration and frequency of smiling.
- UCL ± P individuals reported lower quality of life related to smile esthetics and dental self-confidence.

## Abstract

To investigate the association between clinical, biomechanical, and psychosocial factors and smiling behavior in individuals with treated unilateral cleft lip with or without cleft palate (UCL ± P) compared to non-cleft controls.

Multicenter observational study in New Zealand.

Individuals aged ≥15 (N = 42) comprised 2 study groups: a UCL ± P group (N = 21) and a non-cleft control group (N = 21).

Participants viewed an amusing video while their facial expressions were recorded. Smile features were automatically detected via software. A clinical outcome, nasolabial esthetics, was scored using the Asher-McDade system. Perioral biomechanical properties were measured via myotonometry. Smile Esthetics-related Quality of Life (SERQoL), Orofacial Esthetics Scale (OES), and personality (IPIP-NEO-60) questionnaires were completed.

Smile features and personality traits did not differ between the groups. Participants with UCL ± P exhibited higher stiffness (+44.2%; Cohen's d = 1.6) and tone (+22.6%; Cohen's d = 1.9) at the cleft scar site, and higher decrement (or lower elasticity, +8.5%; Cohen's d = 0.8) adjacent to the scar. Nasolabial esthetics and elasticity of the scar correlated with the duration of smiles and relative smile time (−0.50 < R < −0.44; p < .05). Participants in the UCL ± P group had lower scores for the OES and higher impacts on SERQoL for social contacts and dental self-confidence.

Adolescents and adults with UCL ± P exhibit similar smile behavior as their cleft-free peers—at least in non-social settings. Nasolabial esthetics and perioral biomechanical properties are associated with propensity to smile. UCL ± P is negatively associated with smile-related quality of life and an individual's perception of their facial appearance.